nfs: don't call bdi_unregister
[linux-2.6-block.git] / mm / backing-dev.c
CommitLineData
3fcfab16
AM
1
2#include <linux/wait.h>
3#include <linux/backing-dev.h>
03ba3782
JA
4#include <linux/kthread.h>
5#include <linux/freezer.h>
3fcfab16 6#include <linux/fs.h>
26160158 7#include <linux/pagemap.h>
03ba3782 8#include <linux/mm.h>
3fcfab16
AM
9#include <linux/sched.h>
10#include <linux/module.h>
cf0ca9fe
PZ
11#include <linux/writeback.h>
12#include <linux/device.h>
455b2864 13#include <trace/events/writeback.h>
cf0ca9fe 14
c3c53206
JA
15static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
16
26160158 17struct backing_dev_info default_backing_dev_info = {
d993831f 18 .name = "default",
26160158 19 .ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
26160158
JA
20};
21EXPORT_SYMBOL_GPL(default_backing_dev_info);
cf0ca9fe 22
5129a469
JE
23struct backing_dev_info noop_backing_dev_info = {
24 .name = "noop",
976e48f8 25 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
5129a469 26};
5129a469 27
cf0ca9fe 28static struct class *bdi_class;
cfc4ba53
JA
29
30/*
181387da 31 * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
cfc4ba53
JA
32 * locking.
33 */
03ba3782 34DEFINE_SPINLOCK(bdi_lock);
66f3b8e2 35LIST_HEAD(bdi_list);
03ba3782 36
839a8e86
TH
37/* bdi_wq serves all asynchronous writeback tasks */
38struct workqueue_struct *bdi_wq;
39
018a17bd 40static void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
f758eeab
CH
41{
42 if (wb1 < wb2) {
43 spin_lock(&wb1->list_lock);
44 spin_lock_nested(&wb2->list_lock, 1);
45 } else {
46 spin_lock(&wb2->list_lock);
47 spin_lock_nested(&wb1->list_lock, 1);
48 }
49}
50
76f1418b
MS
51#ifdef CONFIG_DEBUG_FS
52#include <linux/debugfs.h>
53#include <linux/seq_file.h>
54
55static struct dentry *bdi_debug_root;
56
57static void bdi_debug_init(void)
58{
59 bdi_debug_root = debugfs_create_dir("bdi", NULL);
60}
61
62static int bdi_debug_stats_show(struct seq_file *m, void *v)
63{
64 struct backing_dev_info *bdi = m->private;
c1955ce3 65 struct bdi_writeback *wb = &bdi->wb;
364aeb28
DR
66 unsigned long background_thresh;
67 unsigned long dirty_thresh;
68 unsigned long bdi_thresh;
345227d7 69 unsigned long nr_dirty, nr_io, nr_more_io;
f09b00d3
JA
70 struct inode *inode;
71
345227d7 72 nr_dirty = nr_io = nr_more_io = 0;
f758eeab 73 spin_lock(&wb->list_lock);
7ccf19a8 74 list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
c1955ce3 75 nr_dirty++;
7ccf19a8 76 list_for_each_entry(inode, &wb->b_io, i_wb_list)
c1955ce3 77 nr_io++;
7ccf19a8 78 list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
c1955ce3 79 nr_more_io++;
f758eeab 80 spin_unlock(&wb->list_lock);
76f1418b 81
16c4042f
WF
82 global_dirty_limits(&background_thresh, &dirty_thresh);
83 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
76f1418b
MS
84
85#define K(x) ((x) << (PAGE_SHIFT - 10))
86 seq_printf(m,
00821b00
WF
87 "BdiWriteback: %10lu kB\n"
88 "BdiReclaimable: %10lu kB\n"
89 "BdiDirtyThresh: %10lu kB\n"
90 "DirtyThresh: %10lu kB\n"
91 "BackgroundThresh: %10lu kB\n"
c8e28ce0 92 "BdiDirtied: %10lu kB\n"
00821b00
WF
93 "BdiWritten: %10lu kB\n"
94 "BdiWriteBandwidth: %10lu kBps\n"
95 "b_dirty: %10lu\n"
96 "b_io: %10lu\n"
97 "b_more_io: %10lu\n"
98 "bdi_list: %10u\n"
99 "state: %10lx\n",
76f1418b
MS
100 (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
101 (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
f7d2b1ec
JK
102 K(bdi_thresh),
103 K(dirty_thresh),
104 K(background_thresh),
c8e28ce0 105 (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
f7d2b1ec 106 (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
00821b00 107 (unsigned long) K(bdi->write_bandwidth),
f7d2b1ec
JK
108 nr_dirty,
109 nr_io,
110 nr_more_io,
c1955ce3 111 !list_empty(&bdi->bdi_list), bdi->state);
76f1418b
MS
112#undef K
113
114 return 0;
115}
116
117static int bdi_debug_stats_open(struct inode *inode, struct file *file)
118{
119 return single_open(file, bdi_debug_stats_show, inode->i_private);
120}
121
122static const struct file_operations bdi_debug_stats_fops = {
123 .open = bdi_debug_stats_open,
124 .read = seq_read,
125 .llseek = seq_lseek,
126 .release = single_release,
127};
128
129static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
130{
131 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
132 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
133 bdi, &bdi_debug_stats_fops);
134}
135
136static void bdi_debug_unregister(struct backing_dev_info *bdi)
137{
138 debugfs_remove(bdi->debug_stats);
139 debugfs_remove(bdi->debug_dir);
140}
141#else
142static inline void bdi_debug_init(void)
143{
144}
145static inline void bdi_debug_register(struct backing_dev_info *bdi,
146 const char *name)
147{
148}
149static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
150{
151}
152#endif
153
cf0ca9fe
PZ
154static ssize_t read_ahead_kb_store(struct device *dev,
155 struct device_attribute *attr,
156 const char *buf, size_t count)
157{
158 struct backing_dev_info *bdi = dev_get_drvdata(dev);
cf0ca9fe 159 unsigned long read_ahead_kb;
7034ed13 160 ssize_t ret;
cf0ca9fe 161
7034ed13
NJ
162 ret = kstrtoul(buf, 10, &read_ahead_kb);
163 if (ret < 0)
164 return ret;
165
166 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
167
168 return count;
cf0ca9fe
PZ
169}
170
171#define K(pages) ((pages) << (PAGE_SHIFT - 10))
172
173#define BDI_SHOW(name, expr) \
174static ssize_t name##_show(struct device *dev, \
175 struct device_attribute *attr, char *page) \
176{ \
177 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
178 \
179 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
d9e1241e
GKH
180} \
181static DEVICE_ATTR_RW(name);
cf0ca9fe
PZ
182
183BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
184
189d3c4a
PZ
185static ssize_t min_ratio_store(struct device *dev,
186 struct device_attribute *attr, const char *buf, size_t count)
187{
188 struct backing_dev_info *bdi = dev_get_drvdata(dev);
189d3c4a 189 unsigned int ratio;
7034ed13
NJ
190 ssize_t ret;
191
192 ret = kstrtouint(buf, 10, &ratio);
193 if (ret < 0)
194 return ret;
195
196 ret = bdi_set_min_ratio(bdi, ratio);
197 if (!ret)
198 ret = count;
189d3c4a 199
189d3c4a
PZ
200 return ret;
201}
202BDI_SHOW(min_ratio, bdi->min_ratio)
203
a42dde04
PZ
204static ssize_t max_ratio_store(struct device *dev,
205 struct device_attribute *attr, const char *buf, size_t count)
206{
207 struct backing_dev_info *bdi = dev_get_drvdata(dev);
a42dde04 208 unsigned int ratio;
7034ed13
NJ
209 ssize_t ret;
210
211 ret = kstrtouint(buf, 10, &ratio);
212 if (ret < 0)
213 return ret;
214
215 ret = bdi_set_max_ratio(bdi, ratio);
216 if (!ret)
217 ret = count;
a42dde04 218
a42dde04
PZ
219 return ret;
220}
221BDI_SHOW(max_ratio, bdi->max_ratio)
222
7d311cda
DW
223static ssize_t stable_pages_required_show(struct device *dev,
224 struct device_attribute *attr,
225 char *page)
226{
227 struct backing_dev_info *bdi = dev_get_drvdata(dev);
228
229 return snprintf(page, PAGE_SIZE-1, "%d\n",
230 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
231}
d9e1241e
GKH
232static DEVICE_ATTR_RO(stable_pages_required);
233
234static struct attribute *bdi_dev_attrs[] = {
235 &dev_attr_read_ahead_kb.attr,
236 &dev_attr_min_ratio.attr,
237 &dev_attr_max_ratio.attr,
238 &dev_attr_stable_pages_required.attr,
239 NULL,
cf0ca9fe 240};
d9e1241e 241ATTRIBUTE_GROUPS(bdi_dev);
cf0ca9fe
PZ
242
243static __init int bdi_class_init(void)
244{
245 bdi_class = class_create(THIS_MODULE, "bdi");
14421453
AB
246 if (IS_ERR(bdi_class))
247 return PTR_ERR(bdi_class);
248
d9e1241e 249 bdi_class->dev_groups = bdi_dev_groups;
76f1418b 250 bdi_debug_init();
cf0ca9fe
PZ
251 return 0;
252}
76f1418b 253postcore_initcall(bdi_class_init);
cf0ca9fe 254
26160158
JA
255static int __init default_bdi_init(void)
256{
257 int err;
258
839a8e86 259 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
b5c872dd 260 WQ_UNBOUND | WQ_SYSFS, 0);
839a8e86
TH
261 if (!bdi_wq)
262 return -ENOMEM;
263
26160158
JA
264 err = bdi_init(&default_backing_dev_info);
265 if (!err)
266 bdi_register(&default_backing_dev_info, NULL, "default");
976e48f8 267 err = bdi_init(&noop_backing_dev_info);
26160158
JA
268
269 return err;
270}
271subsys_initcall(default_bdi_init);
272
03ba3782
JA
273int bdi_has_dirty_io(struct backing_dev_info *bdi)
274{
275 return wb_has_dirty_io(&bdi->wb);
276}
277
6467716a
AB
278/*
279 * This function is used when the first inode for this bdi is marked dirty. It
280 * wakes-up the corresponding bdi thread which should then take care of the
281 * periodic background write-out of dirty inodes. Since the write-out would
282 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
283 * set up a timer which wakes the bdi thread up later.
284 *
285 * Note, we wouldn't bother setting up the timer, but this function is on the
286 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
287 * by delaying the wake-up.
6ca738d6
DB
288 *
289 * We have to be careful not to postpone flush work if it is scheduled for
290 * earlier. Thus we use queue_delayed_work().
6467716a
AB
291 */
292void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
293{
294 unsigned long timeout;
295
296 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
5acda9d1
JK
297 spin_lock_bh(&bdi->wb_lock);
298 if (test_bit(BDI_registered, &bdi->state))
299 queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
300 spin_unlock_bh(&bdi->wb_lock);
03ba3782
JA
301}
302
cfc4ba53
JA
303/*
304 * Remove bdi from bdi_list, and ensure that it is no longer visible
305 */
306static void bdi_remove_from_list(struct backing_dev_info *bdi)
307{
308 spin_lock_bh(&bdi_lock);
309 list_del_rcu(&bdi->bdi_list);
310 spin_unlock_bh(&bdi_lock);
311
ef323088 312 synchronize_rcu_expedited();
cfc4ba53
JA
313}
314
cf0ca9fe
PZ
315int bdi_register(struct backing_dev_info *bdi, struct device *parent,
316 const char *fmt, ...)
317{
cf0ca9fe 318 va_list args;
cf0ca9fe
PZ
319 struct device *dev;
320
69fc208b 321 if (bdi->dev) /* The driver needs to use separate queues per device */
c284de61 322 return 0;
f1d0b063 323
cf0ca9fe 324 va_start(args, fmt);
19051c50 325 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
cf0ca9fe 326 va_end(args);
c284de61
AB
327 if (IS_ERR(dev))
328 return PTR_ERR(dev);
66f3b8e2 329
cf0ca9fe 330 bdi->dev = dev;
cf0ca9fe 331
03ba3782 332 bdi_debug_register(bdi, dev_name(dev));
500b067c 333 set_bit(BDI_registered, &bdi->state);
c284de61
AB
334
335 spin_lock_bh(&bdi_lock);
336 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
337 spin_unlock_bh(&bdi_lock);
338
455b2864 339 trace_writeback_bdi_register(bdi);
c284de61 340 return 0;
cf0ca9fe
PZ
341}
342EXPORT_SYMBOL(bdi_register);
343
344int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
345{
346 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
347}
348EXPORT_SYMBOL(bdi_register_dev);
349
03ba3782
JA
350/*
351 * Remove bdi from the global list and shutdown any threads we have running
352 */
353static void bdi_wb_shutdown(struct backing_dev_info *bdi)
66f3b8e2 354{
03ba3782
JA
355 if (!bdi_cap_writeback_dirty(bdi))
356 return;
357
358 /*
fff5b85a 359 * Make sure nobody finds us on the bdi_list anymore
03ba3782 360 */
fff5b85a 361 bdi_remove_from_list(bdi);
03ba3782 362
5acda9d1
JK
363 /* Make sure nobody queues further work */
364 spin_lock_bh(&bdi->wb_lock);
365 clear_bit(BDI_registered, &bdi->state);
366 spin_unlock_bh(&bdi->wb_lock);
367
03ba3782 368 /*
839a8e86
TH
369 * Drain work list and shutdown the delayed_work. At this point,
370 * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
371 * is dying and its work_list needs to be drained no matter what.
03ba3782 372 */
839a8e86
TH
373 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
374 flush_delayed_work(&bdi->wb.dwork);
375 WARN_ON(!list_empty(&bdi->work_list));
c0ea1c22 376 WARN_ON(delayed_work_pending(&bdi->wb.dwork));
66f3b8e2
JA
377}
378
592b09a4
JA
379/*
380 * This bdi is going away now, make sure that no super_blocks point to it
381 */
382static void bdi_prune_sb(struct backing_dev_info *bdi)
383{
384 struct super_block *sb;
385
386 spin_lock(&sb_lock);
387 list_for_each_entry(sb, &super_blocks, s_list) {
388 if (sb->s_bdi == bdi)
95f28604 389 sb->s_bdi = &default_backing_dev_info;
592b09a4
JA
390 }
391 spin_unlock(&sb_lock);
392}
393
cf0ca9fe
PZ
394void bdi_unregister(struct backing_dev_info *bdi)
395{
b6875734 396 if (bdi->dev) {
ccb6108f 397 bdi_set_min_ratio(bdi, 0);
455b2864 398 trace_writeback_bdi_unregister(bdi);
8c4db335
JA
399 bdi_prune_sb(bdi);
400
839a8e86 401 bdi_wb_shutdown(bdi);
76f1418b 402 bdi_debug_unregister(bdi);
b6875734 403 device_unregister(bdi->dev);
cf0ca9fe
PZ
404 bdi->dev = NULL;
405 }
406}
407EXPORT_SYMBOL(bdi_unregister);
3fcfab16 408
6467716a
AB
409static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
410{
411 memset(wb, 0, sizeof(*wb));
412
413 wb->bdi = bdi;
414 wb->last_old_flush = jiffies;
415 INIT_LIST_HEAD(&wb->b_dirty);
416 INIT_LIST_HEAD(&wb->b_io);
417 INIT_LIST_HEAD(&wb->b_more_io);
f758eeab 418 spin_lock_init(&wb->list_lock);
839a8e86 419 INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
6467716a
AB
420}
421
e98be2d5
WF
422/*
423 * Initial write bandwidth: 100 MB/s
424 */
425#define INIT_BW (100 << (20 - PAGE_SHIFT))
426
b2e8fb6e
PZ
427int bdi_init(struct backing_dev_info *bdi)
428{
03ba3782 429 int i, err;
b2e8fb6e 430
cf0ca9fe
PZ
431 bdi->dev = NULL;
432
189d3c4a 433 bdi->min_ratio = 0;
a42dde04 434 bdi->max_ratio = 100;
eb608e3a 435 bdi->max_prop_frac = FPROP_FRAC_BASE;
03ba3782 436 spin_lock_init(&bdi->wb_lock);
66f3b8e2 437 INIT_LIST_HEAD(&bdi->bdi_list);
03ba3782
JA
438 INIT_LIST_HEAD(&bdi->work_list);
439
440 bdi_wb_init(&bdi->wb, bdi);
441
b2e8fb6e 442 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
908c7f19 443 err = percpu_counter_init(&bdi->bdi_stat[i], 0, GFP_KERNEL);
04fbfdc1
PZ
444 if (err)
445 goto err;
446 }
447
448 bdi->dirty_exceeded = 0;
e98be2d5
WF
449
450 bdi->bw_time_stamp = jiffies;
451 bdi->written_stamp = 0;
452
7381131c 453 bdi->balanced_dirty_ratelimit = INIT_BW;
be3ffa27 454 bdi->dirty_ratelimit = INIT_BW;
e98be2d5
WF
455 bdi->write_bandwidth = INIT_BW;
456 bdi->avg_write_bandwidth = INIT_BW;
457
20ae0079 458 err = fprop_local_init_percpu(&bdi->completions, GFP_KERNEL);
04fbfdc1
PZ
459
460 if (err) {
461err:
4b01a0b1 462 while (i--)
04fbfdc1 463 percpu_counter_destroy(&bdi->bdi_stat[i]);
b2e8fb6e
PZ
464 }
465
466 return err;
467}
468EXPORT_SYMBOL(bdi_init);
469
470void bdi_destroy(struct backing_dev_info *bdi)
471{
472 int i;
473
ce5f8e77 474 /*
1a1e4530
TH
475 * Splice our entries to the default_backing_dev_info. This
476 * condition shouldn't happen. @wb must be empty at this point and
477 * dirty inodes on it might cause other issues. This workaround is
478 * added by ce5f8e779519 ("writeback: splice dirty inode entries to
479 * default bdi on bdi_destroy()") without root-causing the issue.
480 *
481 * http://lkml.kernel.org/g/1253038617-30204-11-git-send-email-jens.axboe@oracle.com
482 * http://thread.gmane.org/gmane.linux.file-systems/35341/focus=35350
483 *
484 * We should probably add WARN_ON() to find out whether it still
485 * happens and track it down if so.
ce5f8e77
JA
486 */
487 if (bdi_has_dirty_io(bdi)) {
488 struct bdi_writeback *dst = &default_backing_dev_info.wb;
489
f758eeab 490 bdi_lock_two(&bdi->wb, dst);
ce5f8e77
JA
491 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
492 list_splice(&bdi->wb.b_io, &dst->b_io);
493 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
f758eeab
CH
494 spin_unlock(&bdi->wb.list_lock);
495 spin_unlock(&dst->list_lock);
ce5f8e77 496 }
66f3b8e2 497
cf0ca9fe
PZ
498 bdi_unregister(bdi);
499
c0ea1c22 500 WARN_ON(delayed_work_pending(&bdi->wb.dwork));
7a401a97 501
b2e8fb6e
PZ
502 for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
503 percpu_counter_destroy(&bdi->bdi_stat[i]);
04fbfdc1 504
eb608e3a 505 fprop_local_destroy_percpu(&bdi->completions);
b2e8fb6e
PZ
506}
507EXPORT_SYMBOL(bdi_destroy);
508
c3c53206
JA
509/*
510 * For use from filesystems to quickly init and register a bdi associated
511 * with dirty writeback
512 */
b4caecd4 513int bdi_setup_and_register(struct backing_dev_info *bdi, char *name)
c3c53206 514{
c3c53206
JA
515 int err;
516
517 bdi->name = name;
b4caecd4 518 bdi->capabilities = 0;
c3c53206
JA
519 err = bdi_init(bdi);
520 if (err)
521 return err;
522
02aa2a37
KC
523 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
524 atomic_long_inc_return(&bdi_seq));
c3c53206
JA
525 if (err) {
526 bdi_destroy(bdi);
527 return err;
528 }
529
530 return 0;
531}
532EXPORT_SYMBOL(bdi_setup_and_register);
533
3fcfab16
AM
534static wait_queue_head_t congestion_wqh[2] = {
535 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
536 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
537 };
0e093d99 538static atomic_t nr_bdi_congested[2];
3fcfab16 539
1faa16d2 540void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16
AM
541{
542 enum bdi_state bit;
1faa16d2 543 wait_queue_head_t *wqh = &congestion_wqh[sync];
3fcfab16 544
1faa16d2 545 bit = sync ? BDI_sync_congested : BDI_async_congested;
0e093d99
MG
546 if (test_and_clear_bit(bit, &bdi->state))
547 atomic_dec(&nr_bdi_congested[sync]);
4e857c58 548 smp_mb__after_atomic();
3fcfab16
AM
549 if (waitqueue_active(wqh))
550 wake_up(wqh);
551}
552EXPORT_SYMBOL(clear_bdi_congested);
553
1faa16d2 554void set_bdi_congested(struct backing_dev_info *bdi, int sync)
3fcfab16
AM
555{
556 enum bdi_state bit;
557
1faa16d2 558 bit = sync ? BDI_sync_congested : BDI_async_congested;
0e093d99
MG
559 if (!test_and_set_bit(bit, &bdi->state))
560 atomic_inc(&nr_bdi_congested[sync]);
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561}
562EXPORT_SYMBOL(set_bdi_congested);
563
564/**
565 * congestion_wait - wait for a backing_dev to become uncongested
8aa7e847 566 * @sync: SYNC or ASYNC IO
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567 * @timeout: timeout in jiffies
568 *
569 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
570 * write congestion. If no backing_devs are congested then just wait for the
571 * next write to be completed.
572 */
8aa7e847 573long congestion_wait(int sync, long timeout)
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574{
575 long ret;
52bb9198 576 unsigned long start = jiffies;
3fcfab16 577 DEFINE_WAIT(wait);
8aa7e847 578 wait_queue_head_t *wqh = &congestion_wqh[sync];
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579
580 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
581 ret = io_schedule_timeout(timeout);
582 finish_wait(wqh, &wait);
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583
584 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
585 jiffies_to_usecs(jiffies - start));
586
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587 return ret;
588}
589EXPORT_SYMBOL(congestion_wait);
04fbfdc1 590
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591/**
592 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
593 * @zone: A zone to check if it is heavily congested
594 * @sync: SYNC or ASYNC IO
595 * @timeout: timeout in jiffies
596 *
597 * In the event of a congested backing_dev (any backing_dev) and the given
598 * @zone has experienced recent congestion, this waits for up to @timeout
599 * jiffies for either a BDI to exit congestion of the given @sync queue
600 * or a write to complete.
601 *
25985edc 602 * In the absence of zone congestion, cond_resched() is called to yield
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603 * the processor if necessary but otherwise does not sleep.
604 *
605 * The return value is 0 if the sleep is for the full timeout. Otherwise,
606 * it is the number of jiffies that were still remaining when the function
607 * returned. return_value == timeout implies the function did not sleep.
608 */
609long wait_iff_congested(struct zone *zone, int sync, long timeout)
610{
611 long ret;
612 unsigned long start = jiffies;
613 DEFINE_WAIT(wait);
614 wait_queue_head_t *wqh = &congestion_wqh[sync];
615
616 /*
617 * If there is no congestion, or heavy congestion is not being
618 * encountered in the current zone, yield if necessary instead
619 * of sleeping on the congestion queue
620 */
621 if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
57054651 622 !test_bit(ZONE_CONGESTED, &zone->flags)) {
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623 cond_resched();
624
625 /* In case we scheduled, work out time remaining */
626 ret = timeout - (jiffies - start);
627 if (ret < 0)
628 ret = 0;
629
630 goto out;
631 }
632
633 /* Sleep until uncongested or a write happens */
634 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
635 ret = io_schedule_timeout(timeout);
636 finish_wait(wqh, &wait);
637
638out:
639 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
640 jiffies_to_usecs(jiffies - start));
641
642 return ret;
643}
644EXPORT_SYMBOL(wait_iff_congested);
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645
646int pdflush_proc_obsolete(struct ctl_table *table, int write,
647 void __user *buffer, size_t *lenp, loff_t *ppos)
648{
649 char kbuf[] = "0\n";
650
4c3bffc2 651 if (*ppos || *lenp < sizeof(kbuf)) {
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652 *lenp = 0;
653 return 0;
654 }
655
656 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
657 return -EFAULT;
658 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
659 table->procname);
660
661 *lenp = 2;
662 *ppos += *lenp;
663 return 2;
664}